Drier



ly 1952 F. w. GRANTHAM 2 SHEETS-SHEET l .1? jEDEE/(CM m @QAA/THAM,

INVENTOR. a; 106 13 BY f a2 15 IQTTOQNEK July 22, 19:52

F. w. GRANTHAM 2,604,313

DRIER Original Filed Aug. 23, 1945 fsoselcz hf GEANTHAM;

INVENTOR.

HrroeA/EY.

Patented July 22, 1952 DRIER Frederick W. Grantham, Los Angeles, Caiif.

Continuation of application Serial No. 612,227,

August 23, 1945.

1949, Serial No. 108,029

8 Claims. (01. ass-s3) The present invention relates to dryers, and is more particularly directed to dryers which effect their drying function by the direct application of a heated gaseous medium, including the products of combustion furnishing the source of heat, to the mass being dried.

This application is a continuation of an application filed in the name of Frederick W. Grantham, Serial No. 612,227, filed August 23, 1945, for Dryers, later abandoned.

An object of the invention is to provide a relatively compact drying unit having a much greater heat generating capacity for the same size combustion chamber. The comparatively small size of the equipment effects considerable sayings in its cost, and inthe space required for its installation.

Another object of the invention is to prevent gaseous fuel accumulations in the dryer when it is not in use. A further aspect of this phase of the invention is to assure the venting of gas and other explosive substances from the dryer when not in use.

Still another object of the invention is to provide' one or more secondary air openings for effecting cooling of the hot products of combustion down to the desired degree before entering the drying chamber, and to locate such air opening or openings in such position as to allow automatic venting of the dryer when not in use.

A further object of the invention is to prevent the supply of the fuel, such as gas, to the dryer unless certain safety conditions are satisfied.

These may include one or more of the following:

assurance that the dryer door is closed; that the pilot flame is in existence; the provision of an adequate supply of combustion air; proper flow of gas or air to the drying chamber; and operation of an exhaust device for drawing the drying gases through the drying chamber.

Yet another object of the invention is to prevent the temperature of the heating medium supplied to the drying chamber from becoming so high as to cause damage to the dryer and its contents.

This invention possesses many other advantages, and has other objects which may be made more clearly apparent from a consideration of a form in which it may be embodied. This form is shown in the drawings accompanying and forming part of the present specification. It will now be described in detail, for the purpose of illustrating the general principles of the invention; but it is to be understood that such de! tailed description is not to be taken in a limit- This application August 1,

ing sense, since the scope of the invention is best defined by the appended claims.

Referring to the drawings: Figure 1 is a front elevation of a dryer device, embodying the invention; Fig. 2 is a side elevation of the dryer device, including a diagrammatic representation of its control system v Fig. 3 is a diagrammatic view .of the safety control system for the dryer. a

The drying apparatus disclosed in the. drawings may include the usual outer housing Ill enclos-v ing the drying chamber. This chamber is adaptdirections, in a known manner. .:..Access to the drying chamber may be had through a suitable door ll'that may be pivotally supported at its top by means of hinges l2.

The contents of the dryer are adapted to be dried by drawing a heated gaseous medium through the drying chamber. The gaseous medium passes through an inlet conduit l3, com-.- municable with an inlet duct [4 which serves to direct the drying medium into the upper end lfla ofthe dryer housing, from where it passes down through thedryingchamber to its lower portion Hlb, to be exhaustedtherefrom by asuite able. exhaust blower 5.. The gaseous medium and the vaporized substances removed from the contents of the dryer pass outwardly through the blower outlet IBP The blower I5 is rotatable by-an electric motor H, which transmits its rotation to a. driving pulley 18 secured to the motor shaft VI 9,.which is encompassed by a belt 20 passing around'a driven'pulley. 2| attached to the blower shaft 22. Currentmay be supplied to the blower motor through a three-phase line 23.

The heating medium for the dryer is furnished by the combustion of a mixture of a gaseous fuel and air in a combustion chamber 23 connected to the inlet conduit I3; The airwnecessary for combustion is supplied by a combustion air blower ,that may be mounted in'any convenient location, as'on top of the combustion chamber, this blower drawing air into the inlet 25 at its hub portion, and discharging this airthrough its outlet 28 into a mixing chamber 27. The gaseous fuel passes through the main gas line 28, and through an electromagnetically operated safety valve 29,.into the mixing chamber 21, where it is commingled with the air supplied by the blower 24. The air-gas mixture issues from the main 3 burner 30 in the combustion chamber, the products of combustion flowing through the inlet conduit l3 and inlet duct I4 into the upper end |a of a dryer, such flow being assured and assisted by the exhaust blower [5 at the lower end of the dryer.

In order to assure entry of the gaseous heating medium into the dryer at the proper temperature, and to avoid damage to the ductwork l3, l4 that its high temperature might inflict, one or more secondary air inlet openings 3| are provided in the inlet conduit IS. The amount of air entering this opening may be controlled by a suitable disc-like valve 32. This valve 32 is manipulated until sufficient air enters the secondary opening 3| for admixture with the products of combustion emanating from the combustion chamber 23, to bring the mixture of secondary air and combustion products down to the desired temperature for entry into the dryer.

In order to obtain ignition of the air and gas at the main burner 30, a pilot burner 33 is provided. This pilot burner is supplied with a gaseous fuel through a pilot gas line 34 branching from the main gas line 28 in advance of the electromagnetic shut-off valve 29.

The electromagnetic valve 29 may be of any suitable type. As disclosed in Fig. 3, it includes a body 35 having inlet and outlet openings 36, 31, and an intervening seat 38 adapted to be engaged by a valve head 39 to prevent flow of gasthrough the valve and to the mixing chamber 21. This valve 29 is opened by elevating the valve head 39 from the seat 38 whenever current passes through the valve solenoid 40. The passage of such current is dependent upon the satisfaction of certain conditions in the dryer system. In the particular arrangement illustrated in the drawings, current will only pass through the solenoid 40, to open the main valve 29, if the exhaust blower I5 is in operation, if combustion air is being supplied by the blower 24, if the dryer door I is closed, if a pilot flame 4| is in existence at the pilot burner 33, and if the mixture of air and gaseous combustion products is flowing in adequate quantities through the dryer ductwork I3, I4. The invention'does. not necessarily contemplate the. satisfaction of all of the foregoing conditions beforethe main gas valve 29 will open, but it is preferred that all of the foregoing factors be met, or no fuel allowed to pass to the mixing chamber 21 and main burner 39.

To satisfy those conditions, an electrical control circuit is provided. Current from a suitable source may pass through the control circuit leads 42, 43, these leads being connected in series with the valve solenoid 40 and with certain control switches, which may be of the mercury switch type. Thus, the circuit through the main valve solenoid 40 can only be completed if the exhaust blower motor I! is operating and has current passing through it. To satisfy this condition, an electromagnetic relay 44 may be connected across two of the lines 23 leading to the blower motor I! through suitable leads 45. When current is passing to the blower motor II, it is also passing through the relay 44, causing its armature or switch arm 46 to be attracted, and eifecting engagement of this arm 46 with a relay contact 41. One of the control circuit leads 43 is connected to the switch arm 46, and the relay contact 41 is connected through another lead 48 to a mercury switch 49 operated by the dryer door The mercury door switch 49 is open when the dryer door I is open, and is closed when the dryer door is closed. As stated above, the lead 48 from the relay contact 41 is connected to the mercury switch, as to its switch arm 50, which is adapted to engage the switch contact 5| when the door I! is closed. This contact 5| is connected to another switch 52, which will be closed only when a flame 4| is in existence at the pilot burner 33. This switch device 52 includes an electromagnet 53 connected through suitable leads 54 to a thermocouple or thermopile 55 adapted to be energized under the influence of the flame 4| at th pilot burner. Such flame generates a minute current in the thermocouple 55 and energizes the electromagnet 53, moving its armature or switch arm 56 into engagement with a contact 51, to which the lead 58 from the door switch 49 is connected.

The armature 56 is connected by a lead 59 to the contact 60 of a switch 6|, that may be a mercury switch, provided in the inlet duct I4. This switch 6| will be closed if a sufficient blast of air and the products of combustion is passing through the duct l4. As shown diagrammatically in Fig. 3, an arm 62 is pivotally mounted in the duct l4, and is adapted to be moved by the current of air and products of combustion into engagement with the switch contact 60. The arm itself is connected, by means of a lead 63, to another mercury switch 64, which is closed only upon operation of the combustion air blower 24, to supply air to the mixing chamber 21 in sufilcient quantities. This air under pressure can move through a suitable pipe 65 into a chamber 66 having a diaphragm 61 disposed across its walls. When air, under sufficient pressure, is present in the pipe 65 and chamber 66, the diaphragm 61 is moved in one direction, as upwardly in Fig. 3, to move a switch arm 68, connected to the lead 63, into engagement with a contact 69. When the air pressure is too low, or is nonexistent, the diaphragm 61 moves downwardly to open the mercury switch 64.

The contact 69 of the air pressure actuated mercury switch 64 is connected by means of a suitable lead to the solenoid 40, the other end of which is connected to the other maincontrol circuit lead 42.

From the foregoing description of the control circuit, it is apparent that the relay switch 44, door switch 49, pilot switch 52, air blast switch 6|, combustion air switch 64, and the solenoid 40 of the main valve 29 ar all connected in series with one another, and that all switches must be closed before the solenoid can be energized to open the main valve and allow gas to pass to the mixing chamber 21 and main burner 30. Opening of any one of the switches will prevent flow of gas to the main burner, and will immediately stop such flow if the valve is open.

Accordingly, it is apparent that the control circuit will be open and the main valve 29 closed if the exhaust blower motor I! is not operating, if the door I is open, if the pilot flame 4| is not in existence at the pilot burner 33, if a sufiicient blast of air and products of combustion is not passing through the ductwork 3, 4 of th dryer, and if combustion air in adequate quantities and pressure is not being supplied by the air blower All of the above safety system features are important. If the door I l were opened and the gas supply were to continue, the exhaust blower l5 would suck air through the open door of. the housing II, the tumbler opening being of such large size that very little of the products of combustion and secondary air would be drawn through the ductwork and through the dryer. As a result,- the temperature in the ductwork l3, l4 could increase to a dangerously high degree, inasmuch as the burner 30 would continue supplying added heat to the ductwork. Th temperature might be elevated to an extent sufficient to melt, or at least seriouslywarp, the ductwork and damage the dryer to a considerable extend. The provision of the door switch 49. however, insuresthe immediate discontinuance of combustion upon opening of the door H, and prevents the temperature in the dryer from becoming too high.

The requirement that adequate combustion air be-supplied before the main valve 29 can be opened, or can remain open, prevents unburned gaseous fuel from being drawn into and through the-dryer, thereby eliminating an explosion hazard. The diaphragm operated switch 64 will only close if sufiicient combustion air is being supplied for thorough admixture with the gaseous fuel.

If, for some reason, the blast of air and products of combustion at a sufficient velocity is not passing downwardly intothe dryer, as, for example, through development of a leak, the vane operated switch 6| will remain open and prevent opening of the gas valve 29. This switch also prevents opening of the gas valve prior to the supply of adequate volumes of air by the. combustion air blower 24.

Also, the main valve cannot be opened unless the pilot flame 4| is in existence, since the electromagnetically operated switch 52 is in open condition. This insures the presence of a pilot flame to ignite the air-gas mixture at the main burner SD before the main valve can be opened.

Because of the supply of forced combustion air by the blower 24, a large quantity of gas can also be supplied, which is pre-mixed with the combustion air, prior to their discharge through the main burner 30 and burning of the mixture in the combustion chamber 23. As a result, the combustion chamber can be made comparatively small, and, in View of the velocity of the products of combustion passing through the chamber 23, a large quantity of heat can be forced and drawn through the dryer, allowing rapid drying of the contents of the dryer.

The secondary air inlet opening 3| assures the cooling of the combustion products down to a safe and desired temperature. By placing such opening 3| at the top, and the exhaust blower l5 at the bottom of the drying chamber, assurance is not only had that the products of combustion are cooled down sufficiently, but also that gas cannot accumulate in the drying chamber. When the unit is shut down, some unburned products of combustion may be present in the drying chamber. Since the secondary air opening 3| is at the upper portion of the equipment, any combustion products can rise and vent automatically through the opening. Accordingly, when the system is started again, the pilot flame 4| or the flame at the main burner 30 cannot ignite any accumulated gas, which might cause an explosion and damage to the equipment.

The inventor claims:

1. In a dryer: a drying chamber having a door; a combustion chamber; means providing a, passage between said chambers for feeding the products of combustion from the combustion chamber to the upper end of said drying chamber; secondary air inlet openings in said passage. means above said drying chamber for admitting air into said passage means for admixture with said products of combustion; means for withdrawing the mixture of air and combustion products from the lower end of said drying chamber; means for supplying fuel and air to said combustion chamber; a valve for controlling the flow of fuel to said chamber; an electric circuit including a solenoid for opening said valve when said circuit is closed; and means operable by said door upon its opening to open said circuit and effect closing of said valve.

2. In a dryer: a drying chamber having-a door; a combustion chamber; means providing a passage between said chambers for feeding the products of combustion from the combustion chamber to the upper end of said drying chamber; secondary" air inlet openings in said passage means above said drying chamber for admitting air into said passage means for admixture with said products of combustion; means forwithdrawing the mixture of air and combustion products from the lower end of said drying chamber; a supply duct entering said combustion chamber; a, fuel line opening into said duct; a valve in said line; an electricc'i'rcuit including a solenoid for opening saidvalve when said circuit is closed; a blower for supplying air under pressure to said duct for flowing past said fuel line into said combustion chamber; switch means in said circuit responsive to the pressure of air from said blower for opening said circuit upon lowering of said air pressure below a predetermined value; and a switch in said circuit operable by said door, upon opening of said. door, to open said circuit.

3. In a. dryer: a drying chamber; acombustion chamber; means providing a passage between said chambers for feeding the products of combustion from the combustion chamber to the upper end of said drying chamber; said passage means having one or more secondary air inlet openings above said drying chamber for admitting air into said passage means for admixture with said products of combustion; means for withdrawing the mixture of air and combustion products from the lower end of said drying chamber; means for supplying fuel to said combustion chamber; a valve for controlling the flow of fuel to said chamber; and means, operable by said mixture withdrawing means, for controlling operation of said valve.

4. In a dryer: a drying chamber; a combustion chamber; means providing a passage between said chambers for feeding the products of combustion from the combustion chamber to the upper end of said drying chamber; one or more secondary air inlet openings in said passage means above said drying chamber for admitting air into said passage means for admixture with said products of combustion; means for withdrawing the mixture of air and combustion products from the lower end of said drying chamber; means for supplying fuel to said combustion chamber; and means responsive to the flow of fluids through said passage means for admitting fuel to said combustion chamber.

5. In a dryer: a drying chamber; a combustion chamber; means providing a passage between said chambers for feeding the products of combustion from the combustion chamber to the upper end of said drying chamber; one or more secondary air inlet openings in said passage means above said drying chamber for admitting air into said passage means for admixture with said products of combustion; means for withdrawing the mixture of airand combustion products from the lower end of said drying chamber; means for supplying fuel and air to said combustion chamber; and means operable in response to the supply of air to said combustion chamber for controlling the supply of fuel to said combustion chamber.

6. In adryer: a drying chamber; a combustion chamber; means providing a passage between said chambers for feeding the products of combustion from the combustionchamber to the upper end of said drying chamber; one or more secondary air inlet openings in said passage means above said drying chamber for admitting air into said passage means foradmixture with said products of combustion; means for withdrawing the mixture of air and combustion products from the lowerend of said drying chamber; a conduit for supplying fuel to said combustion chamber; a blower for supplying air under pressure to said combustion chamber; a valve in said fuel supply conduit; and means responsive to .the pressure of air from said blower for effecting opening of said valve.

7, Ina dryer: a drying chamber having a door; a combustion chamber; means providing a passage between said chambers for feeding the products of combustion from the combustion chamber to said drying chamber; one or more secondary air inlet openings in said passage means for admitting air into said passage means for admixture with said products of combustion; means for withdrawing the mixture of air and combustion products from said drying chamber; a supply duct entering said combustion chamber; a fuel line opening into said duct; a valve in said line; an electric circuit including a solenoidfor opening said valve when said circuit is closed; a blower for supplying air under pressure to said duct for flowing past said fuel line into said chamber; switch means in said circuit responsive to the pressure of air from said blower for opening said circuit upo'n lowering of said air pressure below a predetermined value; and a switch in said circuit operable by said door, upon opening 01' said door, to open said circuit.

8. In a dryer: a drying chamber; a combustion chamber; means providing apassage between said chambers for feeding the products of combustion from the combustion, chamber to said drying chamber; one or more secondary air inlet openings in said passage means for admitting air into said passage means for admixture with said products of combustion; an exhaust blower for withdrawing the mixture of air and combustion products from said drying chamber; a supply duct entering said combustion chamber; a fuel line opening into said duct; a valve in said line; an electric circuit including a solenoid for opening said valve when said circuit is closed; and switch means in said circuit responsive to operation of said exhaust blower for opening said circuit upon discontinuance of the operation of said exhaust blower.

FREDERICK W. GRANTHAM.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number 

